The invention relates generally to the use of a multi-lead electrode catheter positioned in the epidural space adjacent to the spinal cord to deliver electrical stimulation to a particular group of nerve fibers to control pain by blocking transmission of sensed pain along the nerve and/or spinal cord. More particularly, the invention relates to the use of a wide-range multi-lead electrode catheter having a drug infusion conduit for simultaneous, synergistic application of both electrical stimulation and analgesic medication in acute pain situations, whereby the levels of electrical stimulation and medication infusion needed to block pain sensation are significantly reduced below the levels required when either modality is administered independently. Proper positioning of the multi-lead electrode to provide analgesia for a desired body area covering three to four dermatomes and myotomes is accomplished without fluoroscopic assistance via patient paresthesia response alone.
The use of an epidural catheter for electrical spinal cord stimulation for the management of various conditions of chronic pain has been a proven technique for several decades, and it is in current, wide-spread use. Similarly, the use of an epidural catheter for drug infusion for acute pain management, not only for the relief of suffering, but for the modification of medical and surgical outcome, has been commonly practiced for many years. However, the clinical practice of employing an epidural catheter with the capability of electrical spinal cord stimulation in acute pain situations is unknown. This is because no stimulating epidural catheter currently exists which is practical for acute pain management. Because ease and speed of placement are essential for routine, acute pain therapy applications, the ability to place the catheter without fluoroscopic aid by any physician or nurse anesthetist facile with conventional percutaneous epidural catheter placement is mandatory. The capability of anatomically precise percutaneous placement of a stimulating epidural catheter by electrically stimulated paresthesias alone will greatly enlarge the applicability of the proven technique of electrical spinal cord stimulation for pain management, because severe acute pain states, such as post-operative pain and labor pain, are much more common than severe chronic pain states.
It is known to use local anesthetics and narcotics to control pain sensation in certain acute and chronic pain states by direct infusion of relatively large amounts of these drugs into the epidural space surrounding the spinal cord. This methodology has certain problems however, since the medication dosages required may be relatively large and since numerous significant side effects may occur which are directly proportional in incidence, prevalence and severity to the amount of infused medication. In chronic pain applications, the patients can build up resistance to the beneficial effects of epidural narcotics, necessitating progressively increasing narcotic dosages.
It is also known to moderate or alleviate chronic pain by electrical stimulation of the spinal cord via implantation of an electrode device in the epidural space of the spine. The electrode is positioned by laminectomy and direct visual assessment while the patient is under general anesthesia, or by percutaneous needle placement employing X-ray or fluoroscopic techniques with the patient under local anesthesia. Both methods of implantation require significant time and expense, and as such are impractical and thus not utilized in acute pain situations. positioning with the use of X-ray or fluoroscopy has the added detriment of exposing the patient and implantation team to radiation.
The known electrode devices are typically designed for long-term implantation for relief in chronic pain situations rather than short-term, acute pain situations, such as would be experienced during and after a surgical operation. In particular, the known electrode devices provide an anatomically limited range of stimulation, usually covering only the nerve fibers corresponding to one nerve or dermatome/myotome region, since the designed application is for relief of a particular or localized pain. Because of the limited distribution of the generated electrical field, these electrodes would not be suitable for desensitizing the number of nerve fibers associated with three to four dermatomes and myotomes involving a surgical incision, for example. The known electrode devices also do not provide for simultaneous delivery of drugs to the spinal area, and require fluoroscopic assistance for implantation.
It is an object of this invention to provide method and means for correct, rapid and relatively simple percutaneous insertion and positioning of the dual function epidural electrode catheter without requiring the use of fluoroscopy or general anesthesia by utilizing patient paresthesia response to electrical stimulation alone to determine when the epidural catheter is properly positioned for optimal pain desensitization. The broader electrical field of this device will allow for less precise anatomic placement and therefore this methodology will be employable by any operator qualified in the percutaneous placement of a conventional epidural catheter.
It is a further object of this invention to provide a method and a device for treatment of acute pain conditions by simultaneously administering both electrical stimulation and drug medication to the epidural space and spinal cord. This ability to simultaneously deliver dual modalities allows the level of each individual modality to be reduced below the level necessitated when either modality is independently used, the synergistic combination of the dual modalities providing the required level of analgesia while decreasing or eliminating the adverse side effects of each individual modality.
It is a further object of this invention to provide a method and a device for treatment of acute pain situations by administering electrical stimulation over a broad range of nerve fibers corresponding to at least three to four dermatomes and myotomes, the electrical field thus covering the area of a typical surgical incision and also allowing for less precise anatomic placement.
It is a further object to provide a method and means suitable for use with acute pain situations whereby the ease of implantation allows for its economical use in a variety of acute medical and surgical scenarios, such as perioperative pain, labor pain, acute nonsurgical pain, and limb or graft ischemia.